Emergence of clinical Escherichia coli isolates with decreased susceptibility to ceftazidime and synergic effect with co-amoxiclav due to SHV-1 hyperproduction

J Antimicrob Chemother. 1998 Oct;42(4):535-8. doi: 10.1093/jac/42.4.535.


Between 1994 and 1996 we detected 28 out of 7054 (0.4%) clinical isolates of Escherichia coli with abnormal or reduced inhibition diameters to co-amoxiclav and ceftazidime in a disc diffusion test. The increased MIC of ceftazidime (1-32 mg/L) and the effect of synergy between this antibiotic and co-amoxiclav according to the disc diffusion test suggest the presence of an extended-spectrum beta-lactamase. However, enzymatic characterization and the nucleotide sequence confirm the hyperproduction of the SHV-1 enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amoxicillin-Potassium Clavulanate Combination / pharmacology*
  • Ceftazidime / pharmacology*
  • DNA, Bacterial / analysis
  • Drug Therapy, Combination / pharmacology*
  • Electrophoresis, Gel, Pulsed-Field
  • Escherichia coli / drug effects*
  • Escherichia coli / enzymology
  • Escherichia coli / isolation & purification
  • Humans
  • Isoelectric Focusing
  • Microbial Sensitivity Tests
  • Polymerase Chain Reaction
  • Serotyping
  • Spain
  • beta-Lactamases / biosynthesis*


  • DNA, Bacterial
  • Amoxicillin-Potassium Clavulanate Combination
  • Ceftazidime
  • beta-lactamase PIT-2
  • beta-Lactamases